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M L Rothenberg

Publications and source records attributed to M L Rothenberg.

At least 19 recordsLinked to original sources
PubMed2006

Phase I trial of oral MAC-321 in subjects with advanced malignant solid tumors.

PURPOSE: MAC-321 is a novel taxane that has demonstrated exceptional activity in human xenograft models when administered intravenously and orally. Preclinical studies of MAC-321 have shown antitumor activity in MDR-expressing and paclitaxel-resistant tumors. This phase I dose escalation study was performed to determine the safety, tolerability, and pharmacokinetic profile of orally administered MAC-321 given once every 21 days. Preliminary antitumor activity of MAC-321 was also examined. METHODS: Key eligibility criteria included adult subjects with refractory solid tumors or solid tumors for which conventional therapy was unsuitable or did not exist, good performance status (ECOG ( 2), and adequate hematologic, hepatic, and renal functions. Plasma pharmacokinetic (PK) sampling was performed during the first cycle of therapy. RESULTS: Five dose levels of MAC-321 ranging from 25 to 75 mg/m(2) were evaluated in 18 subjects (four women and 14 men). MAC-321 was well tolerated at the first three dose levels (25, 37, 50 mg/m(2)). Two subjects developed dose-limiting toxicities (DLTs) at 75 mg/m(2); one subject with grade 3 and one subject with grade 4 neutropenia with fever. Three subjects treated at an intermediate dose level of 60 mg/m(2) had no DLTs. However, the study was terminated prior to completion of the maximal tolerated dose cohort after subjects treated with intravenous MAC-321 in a concurrent study experienced life-threatening toxicities. Other common toxicities included grades 1-2 fatigue and grades 1-2 diarrhea. There was substantial interpatient variability in the PK parameters. MAC-321 was rapidly absorbed with a mean C (max) value of less than 1 h. Mean C (max) and AUC values generally increased in a dose-related manner. The median terminal phase elimination half-life was 45 h (range 20-228 h). Disease stabilization was seen in four subjects with the following tumors: mesothelioma (14 cycles), chondrosarcoma (12 cycles), small cell carcinoma (10 cycles), and prostate carcinoma (6 cycles). CONCLUSIONS: MAC-321 can be safely administered orally once every 21 days up to a dose of 60 mg/m(2). The major DLT was neutropenic fever. Four subjects had disease stabilization.

Administration, Oral↗
PubMed2003

Clinical studies in patients with solid tumors using a second-generation antisense oligonucleotide (GEM 231) targeted against protein kinase A type I.

GEM 231 is a second-generation antisense oligonucleotide targeted against the RIalpha regulatory subunit of cAMP-dependent protein kinase type I (PKA-I). Excessive expression of PKA-I is associated with cell proliferation and transformation, and increased levels of secreted extracellular PKA (ECPKA) are found in the serum of cancer patients. Preclinical studies have demonstrated single-agent antitumor activity of GEM 231 in a variety of human cancer xenograft models, and additive or synergistic antitumor activity has been observed with taxane and/or camptothecin-based combinations. Based on prior safety (MTD) data demonstrating dose-dependent, reversible, and cumulative transaminitis, and high peak plasma concentration (Cmax)-dependent changes in activated partial thromboplastin time (aPTT) with GEM 231 2-h twice-weekly infusions, an alternative schedule of GEM 231 given as a single agent was evaluated in patients with advanced solid tumors. Fourteen patients (median age approximately 60 yrs) with advanced solid malignancies received a total of 78 weeks of therapy. GEM 231 was infused via a CADD pump at 80 mg/m2/day (d) for 3 d/wk (n = 1), then for 5 d/wk at 80 (n = 3), 120 (n = 8), and 180 mg/m2/d (n = 2). One cycle was defined as 4 weeks of therapy. Apparent dose dependency for the occurrence of transaminitis was readily reversible. At 180 mg/m2/d, 2 of 2 patients had cycle 1 dose-limiting toxicity (DLT) transaminitis. One patient treated at 120 mg/m2/d experienced grade 3 transaminase elevations after 8 weeks of therapy, but when serum transaminase values rapidly improved he resumed treatment at 80 mg/m2/d for 6 weeks until tumor progression was documented. Another patient at 120 mg/m2/d developed grade 3 esophagitis after 3 weeks, limiting further dosing. One patient (lung cancer) demonstrated stable disease for 9 weeks. Overall, plasma aPTT was minimally prolonged and changes were transient, peaked at the end of each infusion, and were not associated with spontaneous bleeding. A constitutive symptom (e.g., low-grade fatigue) was common, cumulative, and reversible following discontinuation of therapy. Serum ECPKA was measured by enzymatic assay and Western blotting from blood drawn at the beginning and end of each infusion. Serum ECPKA levels demonstrated a trend to decline with the treatment. In addition to single agent schedules, combination trials were undertaken to assess safety and possible interaction of GEM 231 with taxanes (paclitaxel, docetaxel), given once every 3 weeks (one cycle). While trials using the 2-h twice-weekly GEM 231 infusions are ongoing, preliminary results from both studies show that it is safe to combine paclitaxel or docetaxel with GEM 231. Overall, it is also feasible to administer GEM 231 in combination with taxane or nontaxane chemotherapy (e.g., camptothecins). Phase I combination studies are currently underway to further explore the clinical, pharmacokinetic, and biologic profile of GEM 231 with chemotherapy.

Antineoplastic Agents↗
PubMed2002

Phase II trial of 5-fluorouracil plus eniluracil in patients with advanced pancreatic cancer: a Southwest Oncology Group study.

BACKGROUND: Eniluracil is a potent, irreversible inactivator of dihydropyrimidine dehydrogenase, the major catabolic enzyme for 5-fluorouracil (5-FU). Pretreatment with eniluracil significantly increases plasma half-life, plasma concentration and oral bioavailability of 5-FU. This multicenter phase II trial was designed to estimate the 6-month survival rate in patients with metastatic adenocarcinoma of the pancreas treated with 5-FU and eniluracil. PATIENTS AND METHODS: One hundred and sixteen patients (61 with no prior chemotherapy and 55 with prior chemotherapy) were registered for treatment with eniluracil 50 mg (total dose) p.o. on days 1-7 and 5-FU 20 mg/m(2)/day p.o. on days 2-6 of a 28-day treatment cycle. RESULTS: In 106 patients evaluable for survival, the 6-month survival rate was 34% [95% confidence interval (CI) 22% to 47%, median survival 3.6 months] for patients who had not been treated previously with chemotherapy and 29% (95% CI 16% to 42%, median survival 3.4 months) for those who had received prior chemotherapy. For those patients with measurable disease, the confirmed response rates were 8% and 2%, respectively. The most common grade 3-4 toxicities were neutropenia (29% of patients) and diarrhea (12% of patients). Overall, 69% of patients experienced a grade 3 or worse adverse event during treatment. CONCLUSIONS: These results suggest that the combination of a 7-day course of eniluracil and a 5-day course of oral 5-FU has limited activity in patients with advanced pancreatic cancer, and is associated with a high frequency of clinically significant adverse events.

Adenocarcinoma↗
PubMed2001

Mortality associated with irinotecan plus bolus fluorouracil/leucovorin: summary findings of an independent panel.

PURPOSE: To review and assign attribution for the causes of early deaths on two National Cancer Institute-sponsored cooperative group studies involving irinotecan and bolus fluorouracil (5-FU) and leucovorin (IFL). PATIENTS AND METHODS: The inpatient, outpatient, and research records of patients treated on Cancer and Leukemia Group B protocol C89803 and on North Center Cancer Treatment Group protocol N9741 were reviewed by a panel of five medical oncologists not directly involved with either study. Each death was categorized as treatment-induced, treatment-exacerbated, or treatment-unrelated. RESULTS: The records of 44 patients who experienced early deaths on C89803 (21 patients) or N9741 (23 patients) were reviewed. Patients treated with irinotecan plus bolus 5-FU/leucovorin had a three-fold higher rate of treatment-induced or treatment-exacerbated death than patients treated on the other arm(s) of the respective studies. For C89803, these rates were 2.5% (16 of 635) for IFL versus 0.8% (five of 628) for bolus weekly 5-FU and leucovorin. For N9741, these rates were 3.5% (10 of 289) for IFL, 1.1% (three of 277) for oxaliplatin plus bolus and infusional 5-FU and leucovorin, and 1.1% (three of 275) for oxaliplatin plus irinotecan. Multiple gastrointestinal toxicities that often occurred together were characterized into a gastrointestinal syndrome. Sudden, unexpected thromboembolic events were characterized as a vascular syndrome. The majority of deaths in both studies were attributable to one or both of these syndromes. CONCLUSION: Close clinical monitoring, early recognition of toxicities and toxicity syndromes, aggressive therapeutic intervention, and withholding therapy in the presence of unresolved drug-related toxicities is recommended for patients receiving IFL or other intensive chemotherapy regimens.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Phase II trial of oral altretamine for consolidation of clinical complete remission in women with stage III epithelial ovarian cancer: a Southwest Oncology Group trial (SWOG-9326).

OBJECTIVE: The aim of this study was to evaluate the 2-year survival rate in a group of women in complete clinical remission (cCR) from Stage III ovarian cancer following front-line therapy who were then treated with a 6-month course of altretamine. METHODS: Patients were documented to be in cCR by physical examination, computed tomography or magnetic resonance imaging scan, and serum CA-125. Treatment consisted of altretamine (Hexalen) 260 mg/m(2)/day po divided into four doses taken after meals and at bedtime for 14 of 28 days for six cycles. Based on previous experience in the Southwest Oncology Group, the treatment would be considered promising if the 2-year survival rate was > or = 65% as measured from study registration. RESULTS: From 9/1/93 and 7/1/97, 112 patients were registered and 97 were fully evaluable. The majority of patients had optimally debulked (< or = 1 cm: 63%), high-grade (Grade 3: 82%) tumors. The 2-year survival rate in this study was 75% (95% CI: 66-84%). For those patients with optimal disease, the 2-year survival rate was 82% (95% CI: 72-92%) and for those with suboptimal disease it was 64% (95% CI: 48-79%). Four patients (4%) experienced Grade 4 and 21 patients (22%) experienced Grade 3 toxicities consisting primarily of nausea/vomiting, neutropenia, fatigue, anxiety, and paresthesias. CONCLUSIONS: The 2-year survival rate in this study warrants further evaluation of consolidation therapy for women in clinical complete remission following front-line chemotherapy for Stage III ovarian cancer. Caution is advised in the interpretation of these data, however, because of the nonrandomized nature of the trial and the unknown contribution of front-line use of paclitaxel to the durability of clinical complete response.

Administration, Oral↗
PubMed2001

A phase II study of irinotecan with 5-fluorouracil and leucovorin in patients with previously untreated gastric adenocarcinoma.

BACKGROUND: A phase II study testing the safety and efficacy of irinotecan (CPT-11). 5-fluorouracil (5-FU), and leucovorin (LCV) was conducted in patients with advanced gastric adenocarcinomas. PATIENTS AND METHODS: Patients with metastatic or recurrent adenocarcinoma of the gastroesophageal junction (GEJ) or stomach were entered onto this study. Previous chemotherapy for metastatic disease was not allowed. Treatment consisted of repeated 6-week cycles comprising CPT-11 125 mg/m2 intravenously (i.v.) followed immediately by LCV 20 mg/m2 i.v. and 5-FU 500 mg/m2 i.v., all given weekly for four weeks followed by a two-week rest. RESULTS: Thirty-eight patients were enrolled and 36 eligible patients received protocol therapy. Grade 3-5 toxicities consisted primarily of neutropenia (36%) and diarrhea (28%). Neutropenic infection was observed in 14% of patients, with 3 (8%) dying of neutropenic sepsis. The overall response rate was 22% (95% confidence interval [CI] 8.5% to 35.5%). Median survival was 7.6 months, and median time to progression was 4.4 months. CONCLUSION: This weekly regimen of CPT-11 with bolus 5-FU/LCV is active in patients with advanced adenocarcinomas of the stomach or gastroesophageal junction. While rates of grade 3-4 neutropenia and diarrhea were similar to those observed historically in patients receiving this regimen for colorectal cancer, neutropenic fever/sepsis appeared to be more frequent, and dose modifications were substantial. Future trials of this combination in patients with gastric cancer should decrease the absolute starting drug doses and/ or employ altered scheduling that better accommodates the pattern of toxicity.

Adenocarcinoma↗
PubMed2001

Phase I dose-finding and pharmacokinetic trial of irinotecan (CPT-11) administered every two weeks.

OBJECTIVES: This trial was performed to determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetic profile of irinotecan (CPT-11) when administered on a once-every-2-week schedule. PATIENTS AND METHODS: CPT-11 was administered to successive cohorts of patients at progressively increasing starting doses ranging from 125 to 350 mg/m2. The MTD and DLTs were determined both for CPT-11 alone and for CPT-11 followed by filgrastim (G-CSF). Plasma samples were obtained during the first 24 hours after initial dosing to determine the total concentrations (lactone + carboxylate forms) of CPT-11; of the active metabolite SN-38; and of SN-38 glucuronide (SN-38G). RESULTS: Neutropenic fever was the DLT for CPT-11 at the 300 mg/m2 dose level. When G-CSF was added, dose escalation beyond 350 mg/m2 could not be achieved due to grade 2-3 toxicities that prevented on-time retreatment with CPT-11. Severe, late diarrhea was uncommon on this schedule. Peak plasma concentrations of SN-38 and SN-38G were approximately 2.5% and 4.2% of the corresponding peak plasma concentration for CPT-II, respectively The harmonic mean terminal half-lives for CPT-11, SN-38, and SN-38G were 7.1 hours, 13.4 hours, and 12.7 hours, respectively. No predictive correlation was observed between CPT-11 or SN-38 peak concentration or AUC and first-cycle diarrhea, neutropenia, nausea, or vomiting. Across the range of doses studied, mean CPT-11 clearance was 14.0 +/- 4.0 l/h/m2 and volume of distribution was 146 +/- 45.9 l/m2. CONCLUSIONS: When administered every two weeks, the recommended phase II starting dose of CPT-11 is 250 mg/m2 when given alone and 300 mg/m2 when supported by G-CSF. This every-two-week regimen offers a tolerable and active alternative to weekly or every-three-week single-agent CPT-11 therapy.

Adult↗
PubMed2001

Irinotecan (CPT-11): recent developments and future directions--colorectal cancer and beyond.

Since its approval in the United States in 1996, irinotecan (CPT-11, Camptosar, Pharmacia Corp.; Peapack, NJ) has undergone extensive clinical evaluation. In the past five years, the focus of development has evolved from evaluation of single-agent activity in refractory disease settings to evaluation of front-line irinotecan-based combination chemotherapy regimens and integration of irinotecan into combined modality regimens. Important studies have been performed clarifying the role of irinotecan in treating colorectal and other gastrointestinal cancers, small cell and non-small cell lung cancer, and a variety of other malignancies. Preclinical studies performed in conjunction with these clinical trials have also provided significant insights into the pharmacology, metabolism, mechanisms of resistance, and molecular determinants of response. This review summarizes that progress, focusing on the achievements of the past five years.

Antineoplastic Agents, Phytogenic↗
PubMed2000

Matrix metalloproteinases: biologic activity and clinical implications.

Tumor progression is a complex, multistage process by which a normal cell undergoes genetic changes that result in phenotypic alterations and the acquisition of the ability to spread and colonize distant sites in the body. Although many factors regulate malignant tumor growth and spread, interactions between a tumor and its surrounding microenvironment result in the production of important protein products that are crucial to each step of tumor progression. The matrix metalloproteinases (MMPs) are a family of degradative enzymes with clear links to malignancy. These enzymes are associated with tumor cell invasion of the basement membrane and stroma, blood vessel penetration, and metastasis. They have more recently been implicated in primary and metastatic tumor growth and angiogenesis, and they may even have a role in tumor promotion. This review outlines our current understanding of the MMP family, including the association of particular MMPs with malignant phenotypes and the role of MMPs in specific steps of the metastatic cascade. As scientific understanding of the MMPs has advanced, therapeutic strategies that capitalize on blocking the enzymes have rapidly developed. The preclinical and clinical evolution of the synthetic MMP inhibitors (MMPIs) is also examined, with the discussion encompassing important methodologic issues associated with determining clinical efficacy of MMPIs and other novel therapeutic agents.

Animals↗
PubMed2000

Efficacy of oxaliplatin in the treatment of colorectal cancer.

Colorectal cancer is one of the leading causes of cancer death. The mainstay of chemotherapy in colorectal cancer patients for the past 40 years has been fluorouracil (5-FU). Oxaliplatin (Eloxatin) is a novel platinum compound with promising activity in colorectal cancer. As a single agent, oxaliplatin has produced response rates of 12% to 24% in patients with previously untreated advanced colorectal cancer, and 10% to 11% in patients with relapsed or refractory advanced colorectal cancer. In phase II trials, oxaliplatin combined with 5-FU, with or without leucovorin, was associated with response rates of 60% and higher when used as front-line therapy, and when used in patients with relapsed or refractory advanced colorectal cancer, response rates ranged from 25% to 50%. In the front-line setting, two randomized trials of 5-FU and leucovorin, with or without oxaliplatin, demonstrated that the addition of oxaliplatin significantly increases response rate and time to tumor progression, but not survival, over 5-FU plus leucovorin alone. The reasons for this discrepancy are unclear, and several possibilities are being considered. Additional phase III trials are underway to clarify the contribution of oxaliplatin in the treatment of patients with locally advanced and metastatic colorectal cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1999

An investigational new drug treatment program for patients with gemcitabine: results for over 3000 patients with pancreatic carcinoma.

BACKGROUND: An Investigational New Drug (IND) treatment program allows patients access to a drug that has shown activity against a serious or life-threatening disease prior to full Food and Drug Administration (FDA) review and approval. This treatment IND program, in which patients with locally advanced or metastatic pancreatic carcinoma were treated with gemcitabine, began in 1995. METHODS: Eligibility criteria were < or =1 prior chemotherapy regimen; a Karnofsky performance status (KPS) of > or =50; and adequate bone marrow, liver, and renal function. Gemcitabine was given at a dose of 1000 mg/m2 weekly x 7 followed by a week of rest, then weekly x 3 every 4 weeks thereafter. In this program, disease-related symptom improvement (DRSI) was defined retrospectively as 1) improvement in pain (on a 7-point scale) and/or analgesic class (e.g., morphine improving to codeine) and/or KPS (> or =20 points), or 2) stability of these three parameters with a 7% increase in weight from baseline. RESULTS: A total of 3023 patients enrolled. At baseline, 80% of them had Stage IV disease, and 84% had a baseline KPS > or = 70. The median age was 65 years, and 56% of the patients were male. The cumulative DRSI response rate after the fourth cycle was 18.4%. Of 982 patients with tumor response data, there were 14 with complete response and 104 with partial response, for an overall response rate of 12.0% (95% confidence interval [CI], 10.0-14.0%). For 2380 patients with survival data, the median survival was 4.8 months (95% CI, 4.5-5.1 months) and the 12-month survival was 15%. Gemcitabine was well tolerated; only 4.6% of discontinuations were due to adverse events. CONCLUSIONS: Notable disease-related symptom improvement and survival were seen with gemcitabine in this large, compassionate-use setting, and these findings were in agreement with those of earlier registration trials.

Aged↗
PubMed1999

A multicenter, phase II trial of weekly irinotecan (CPT-11) in patients with previously treated colorectal carcinoma.

BACKGROUND: This multicenter, Phase II trial was performed to evaluate the antitumor activity and toxicity of irinotecan (CPT-11) in patients with metastatic colorectal carcinoma that had recurred or progressed after 5-fluorouracil (5-FU)-based chemotherapy. METHODS: CPT-11 was given as a 90-minute intravenous infusion in repeated 6-week (42-day) courses comprising weekly treatment for 4 consecutive weeks followed by a 2-week rest. Tumor measurements were obtained after every second course of therapy. Toxicity was assessed weekly using the National Cancer Institute Common Toxicity Criteria. RESULTS: A total of 166 patients were entered into the trial. The first 64 patients received a starting dose of 125 mg/m2. An additional 102 patients were enrolled at a starting dose of 100 mg/m2 to determine whether a reduction in the starting dose would result in lower toxicity without sacrificing efficacy. Objective responses to CPT-11 were observed in 18 patients (1 complete response and 17 partial responses) (response rate [RR] = 10.8%; 95% confidence interval [CI], 6.1-15.6%). An additional 67 patients (40.4%) had stable disease as their best response. At the 125 mg/m2 starting dose, the RR was 14.1% (9 of 64 patients; 95% CI, 5.5-22.6%). Among patients given a starting dose of 100 mg/m2, the RR was 8.8% (9 of 102 patients; 95% CI, 3.3-14.3%). The overall median survival was 9.9 months (range, 0.3-36.8 months). The most frequently observed Grade 3/4 toxicities were gastrointestinal events (i.e., diarrhea [27.1%], nausea [15.1%], emesis [9.6%], abdominal cramping [22.2%], and neutropenia [19.9%]). There were no significant differences in the frequencies of Grade 3/4 toxicities between the 125 mg/m2 and 100 mg/m2 starting dose levels except for Grade 3/4 emesis (21.9% vs. 2%; P < 0.001). Patients age > or = 65 years were twice as likely (38.6% vs. 18.8%; P < 0.008) to develop Grade 3/4 diarrhea compared with younger patients when all courses of therapy were evaluated. However, older age did not significantly predict for a higher incidence of first-course diarrhea (25.0% vs. 14.7%; P = 0.106). CONCLUSIONS: CPT-11 can induce tumor regression in patients with metastatic colorectal carcinoma that has progressed during or shortly after 5-FU-based chemotherapy. Gastrointestinal events and neutropenia were the most common serious toxicities. Given the trend toward a higher response rate without substantially greater toxicity, 125 mg/m2 has been selected as the preferred starting dose for further studies. Careful attention to appropriate CPT-11 dose modification and early intervention with loperamide may be especially important in elderly patients.

Adult↗
PubMed1999

Phase I and pharmacokinetic trial of oral irinotecan administered daily for 5 days every 3 weeks in patients with solid tumors.

PURPOSE: We conducted a phase I dose-escalation trial of orally administered irinotecan (CPT-11) to characterize the maximum-tolerated dose (MTD), dose-limiting toxicities (DLTs), pharmacokinetic profile, and antitumor effects in patients with refractory malignancies. PATIENTS AND METHODS: CPT-11 solution for intravenous (IV) use was mixed with CranGrape juice (Ocean Spray, Lakeville-Middleboro, MA) and administered orally once per day for 5 days every 3 weeks to 28 patients. Starting dosages ranged from 20 to 100 mg/m2/d. RESULTS: Grade 4 delayed diarrhea was the DLT at the 80 mg/m2/d dosage in patients younger than 65 years of age and at the 66 mg/m2/d dosage in patients 65 or older. The other most clinically significant toxicity of oral CPT-11 was neutropenia. A linear relationship was found between dose, peak plasma concentration, and area under the concentration-time curve (AUC) for both CPT-11 and SN-38 lactone, implying no saturation in the conversion of irinotecan to SN-38. The mean metabolic ratio ([AUC(SN-38 total) + AUC(SN-38G total)]/AUC(CPT-11 total)) was 0.7 to 0.8, which suggests that oral dosing results in presystemic conversion of CPT-11 to SN-38. An average of 72% of SN-38 was maintained in the lactone form during the first 24 hours after drug administration. One patient with previously treated colorectal cancer and liver metastases who received oral CPT-11 at the 80 mg/m2/d dosage achieved a confirmed partial response. CONCLUSION: The MTD and recommended phase II dosage for oral CPT-11 is 66 mg/m2/d in patients younger than 65 years of age and 50 mg/m2/d in patients 65 or older, administered daily for 5 days every 3 weeks. The DLT of diarrhea is similar to that observed with IV administration of CPT-11. The biologic activity and favorable pharmacokinetic characteristics make oral administration of CPT-11 an attractive option for further clinical development.

Administration, Oral↗
PubMed1999

DNA topoisomerase I-targeting drugs as radiation sensitizers.

Combination chemoradiation, alone or as an adjuvant to surgery, has been shown to improve treatment outcomes in a number of human malignancies, but may be limited by normal tissue toxicities. A primary challenge in radiation oncology is the development of drugs that can selectively enhance the cytotoxicity of ionizing radiation against tumor cells. Mammalian DNA topoisomerase I is the major cytotoxic target of a number of newly developed anticancer drugs that have shown efficacy against solid tumors, including colon cancer, ovarian cancer, lung cancer, cancer of the head and neck, and pediatric cancers. Topoisomerase I-targeting drugs exert their cytotoxic effect by producing enzyme-mediated DNA damage, rather than by directly inhibiting enzyme catalytic activity. DNA topoisomerase I recently has been established as a biochemical mediator of radiosensitization in cultured mammalian cells by camptothecin derivatives. Interestingly, this sensitization appears to be schedule-dependent, cell cycle phase-specific, cell line-dependent, and not strictly dependent on drug cytotoxicity. Clinical chemoradiation trials using camptothecin derivatives are currently ongoing. Future studies aimed at better understanding the underlying mechanisms of molecular radiosensitization with topoisomerase I-targeting drugs are pivotal to the clinical application of these agents, as well as in guiding the development of more effective radiosensitizers.

Animals↗
PubMed1999

Topoisomerase I inhibitors in the treatment of colorectal cancer.

Over the past 10 years, a number of topoisomerase I inhibitors have entered into clinical trials and several of these have been evaluated in phase II and III studies to determine their activity in patients with advanced colorectal cancer. The most extensively studied of these has been irinotecan (CPT-II). In phase II trials in patients with colorectal cancer that was recurrent or refractory to 5-Ruorouracil (5-FU)based front-line therapy, response rates of 14% to 22% and median survival times of 8 to 10 months have been consistently reported by groups from Japan, Europe, and the United States using avariety of drug administration schedules Two recently reported phase III trials comparing CPT-II against infusional 5-FU or best supportive care demonstrated that CPT-II confers a survival advantage over either of the two other approaches. In front-line treatment of colorectal cancer, CPT-II produces response rates of 19% to 32% and median survival times of 11 to 12 months, figures quite similar to those achievable with bolus 5-FU and leucovorin. Further evaluation in the front-line setting has concentrated on the integration of CPT-II with 5-FU-based regimens. The role of other topoisomerase I inhibitors in colorectal cancer has been more difficult to characterize. Using a standard daily x 5 schedule, topotecan has little objective activity against relapsed or refractory colorectal cancer. Infusional topotecan appears more promising in the treatment of patients with advanced colorectal cancer. The development of an oral formulation of topotecan may make this approach more feasible and is likely to undergo dinical evaluation in the near future. Phase II evaluation of 9-aminocamptothecin (9-AC) has focused on infusional schedules of varying lengths Despite this, little antitumor activity has been observed against colorectal cancer. Other topoisomerase I inhibitors, such as DX-8951f and 9-nitrocamptothecin (9-NC, RFS2000), have not been formally tested in phase II trials against colorectal cancer. In summary, extensive evaluation of topoisomerase I inhibitors has identified a significant degree of variability in clinical activity in patients with advanced colorectal cancer. To date, only one topoisomerase I inhibitor, CPT-II, has demonstrated a level of activity sufficient for it to become an integral component of treatment for patients with 5-FU-refractory colorectal cancer. Current and future studies will focus on the development of front-line regimens combining CPT-II and 5-FU for treatment of patients with advanced-stage disease, moving topoisomerase I inhibitors into the adjuvant therapy setting, and developing combined modality regimens of surgery, radiation, and topoisomerase I inhibitors for patients with locally advanced colorectal cancer.

Animals↗